1. Field of the Invention
This invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus which have the electrophotographic photosensitive member.
2. Related Background Art
A number of methods as disclosed in U.S. Pat. No. 2,297,691 and Japanese Patent Publications No. 42-23910 and No. 43-24748 are conventionally known as electrophotography. In general, copies are obtained by forming an electrostatic latent image on a photosensitive member by utilizing a photoconductive material and by various means, subsequently developing the latent image by the use of a developer (hereinafter "toner"), and transferring the toner as a toner image to a transfer medium such as paper as occasion calls, followed by fixing by means of a heat roller or the like.
The step of forming an electrostatic latent image in this electrophotographic process is, stated in greater detail, a step where a photosensitive member surface constituted of a-Se, a-Si or an organic photoconductive material is charged uniformly by corona charging, or contact charging making use of a conductive roller, and thereafter an optical image of a copying original or a dot pattern formed by the action of laser light is exposed to form the electrostatic latent image. In this charging step, active substances such as ozone and NO.sub.x are known to be generated. Also, in some cases, active substances such as ions are contained in transfer mediums such as paper.
However, the ozone and NO.sub.x generated in the above step and the active substances contained in transfer mediums may act on the photosensitive member to cause a variation of potential and an increase in residual potential, and may adversely affect electrophotographic performance and images to cause, e.g., unfocused images and smeared images and cause a lowering of running performance of the photosensitive member. In particular, organic material photosensitive members have a low resistance to ozone and NO.sub.x and moreover are often used under negative charging, which is causative of ozone in a large quantity. Thus, the generation of ozone and NO.sub.x is a great problem. Also, the active substances contained in transfer mediums may cause poor development.
To solve such problems, proposals are made on methods such that (1) a fan is provided in the machine body to exhaust any problem-causing substances, (2) a process is introduced by which any deteriorated portions of the photosensitive member surface can always be removed, (3) organic photoconductive materials resistant to the active substances as stated above are selected and (4) an antioxidant or an anti-deterioration agent is added in the photosensitive member. However, the method (1) has a problem on exhaustion efficiency; (2), a problem on mechanical durability of the photosensitive member; and (3) and (4), a problem of a difficulty in achieving both the durability to active substances and the performance of the photosensitive member.